Increasing production and inadequate management of plastic waste have resulted in the accumulation of plastic debris in the global biogeochemical cycles. In natural environments, these plastics become micronized by various physicochemical reactions, leading to the formation of microplastics. This review provides a concise literature account of the current state of MP contamination in sea sediments worldwide. We report on the capacity of the adopted sampling, pretreatment, and identification methods and provide recommendations for sustainable long-term deep-sea sediment monitoring programs. Our systematic review showed that for MP contamination in marine sediments, the number density of MPs with a minimum particle size of 0.1 mm ranges from 10 to 1,000 items/kg-dry weight. On the other hand, the number density of MPs with a minimum particle size of 0.01 mm ranges from 100 to 10,000 items/kg-dry weight. In all 31 papers analyzed, the percentage of fragments and fibers was over 50%. Polyethylene, used in containers and packaging, and polyester, a fiber used in clothing, were the most common polymer components. Analysis of sediment cores can reveal the history of MPs contamination. In addition, the deep-sea sediments have been identified as the endpoints of MPs that occur in the environment.

This study is aimed at investigating the poisoning effect of sulphide on methanogenic cultures. Using cultures enriched with either acetate or formate as a sole electron donor, sets of 1-week batch inhibition tests were performed to analyse the dynamic change of the living microorganism concentrations under the varied sulphide concentrations between zero and 400 mg-S L⁻¹. In both cultures, the cellular decay was doubled when the cultures were placed in 100 mg-S L^–1 of total sulphide. When the cultures were exposed to higher sulphide, higher specific decay rates were obtained. Because of the low correlations of the unionised sulphide concentrations to the specific decay rates, the total sulphide concentration was thought to be the dominant inhibition factor rather than its unionised form. To express the acceleration of cellular decay, a mathematical model was developed. Since the decay phenomena of both cultures were quite similar to each other, a culture-wide empirical formula was obtained to calculate the specific decay rate. In the model equation, the specific decay rate of the methanogenic cultures was linearly expressed with a coefficient of 0.30∙10⁻³ ± 0.05∙10⁻³ mg-S⁻¹ L d⁻¹ for sulphide concentration and a coefficient of 0.044 ± 0.013 d^–1 for the inherent specific decay rate.

The current study examines the effects of vitamin C nanoparticles on fish health as well as the acute and long-term toxic effects of Fe²⁺ and Mn²⁺ combination on Nile tilapia, Oreochromis niloticus. The metal mixture under study has a detected 96-hour LC₅₀ of 2.7% TU (Toxic unit). Fish were divided into four groups: Group 1, which served as the control group; Groups 2, 3, and 4 were exposed to 20% of the 96-hour LC₅₀ for 30 days and fed on a conventional diet. Fish of Group 3 were supplemented with 20% vitamin C while fish of Group 4 were supplemented with 20% vitamin C as nanoparticles. The metals^, levels in tissues of the liver and gills were examined, as well as the biochemical markers of metabolic processes in blood plasma. Fish from Group 2 displayed noticeable deteriorating conditions, followed by those from Group 3, whereas fish from Group 4 demonstrated noticeable good conditions across all examined criteria. Results showed that, while vitamin C nanoparticle proved to be more efficient, both vitamin C and its nanoparticles supplements had a positive impact on reducing the harmful effects of the studied metal mixture by chelating metal ions and scavenging free radicals.

The objective of this study is to identify the primary watershed management strategies for the Shulabad Watershed in Lorestan Province, aiming to enhance health status and service development. To this end, an examination was conducted on the key sources of income and economic status of watershed residents, and the most significant environmental challenges stemming from existing economic activities were identified. Subsequently, the strength, weakness, opportunities, and threat (SWOT) framework was utilized for strategy identification. The quantitative strategic planning matrix (QSPM) technique was applied for their prioritization. The Delphi technique was employed to ascertain the relative weights of these factors. Considering these factors, strategies were devised for achieving management objectives by pairing each internal and external factor. The final attractiveness of each strategy was determined using the QSPM model, which also aided in prioritizing different strategies. The findings revealed that the strategy involving the development of alternative livelihood activities to alleviate pressure on natural resources, with an attractiveness score of 12.28, was deemed the most effective for the Shulabad Watershed. Implementation of strategies stemming from this research not only stands to enhance sustainable services in selected watersheds but also promises to ameliorate the health status of these watersheds.